Selection of desulfurization agents for PSA systems?
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Gentle experts. The CO gas is purified using semi-water gas from the ammonia synthesis system through a PSA system. The semi-water gas among them has already undergone preliminary desulfurization. Upon arrival at PSA, the inorganic sulfur (expressed as H2S) was around 100 ppm, while the organic sulfur (expressed as COS) was between 100 and 200 ppm. It passes through a precision desulfurization system before entering PSA-I. What desulfurization process is generally used? What desulfurizing agents do you use, and what is their actual effectiveness? I really want to know! Please share your experience!
For this type of operating condition (low sulfur content), dry desulfurization agents at room temperature are generally recommended. If the system contains oxygen but no organic sulfur, activated carbon or iron oxide can be used; if there is oxygen along with organic sulfur, it is best to opt for activated carbon-based desulfurization agents. In the absence of oxygen and organic sulfur, activated carbon can only be used for desulfurization; iron oxide is recommended in such cases. When there is no oxygen but organic sulfur is present, stepwise desulfurization or desulfurizing agents such as zinc oxide at moderate temperatures must be used. Due to adsorption or reaction, little sulfur is present at the outlet when it is first put into use; after being in operation for some time, and as long as the required accuracy standards are met, those with a higher sulfur capacity have an advantage.
Since it is before pressure swing adsorption, dry desulfurization is the preferred method; moreover, if the sulfur content in your carbon monoxide gas is not too high, desulfurization may not even be necessary, as pressure swing adsorption can remove the vast majority of sulfur compounds. It can reach several PPM levels
Before entering the PSA process in our plant, activated carbon is used for desulfurization; to achieve more effective desulfurization, ZnO is a better choice as it provides better results. However, it is important to pay attention to the pressure drop, because if the pressure drop is high after desulfurization, the adsorption efficiency in the PSA process will be poor. It is best to keep the pressure above the specified operating value. In PSA, H2S is adsorbed, which is harmful to subsequent processes such as compressors or catalysts; therefore, desulfurization is necessary before the gas enters the PSA unit. In our plant, the H2S level in the gas entering the PSA process is kept at 0.1 mg/m3. This post was last edited by chc1125 on 2008-11-17 14:19.]
ZnO can remove both organic sulfur and inorganic sulfur; precision desulfurization usually relies on it, while activated carbon is used for rough desulfurization. Nowadays, some manufacturers produce improved versions of activated carbon that also offer excellent desulfurization performance. Generally, PSA system designers provide high-efficiency desulfurizing agents to meet the sulfur requirements of the subsequent processes in the PSA system.
If the content of the raw material gas stream is 3 g/NM3, can it be fed directly into the PSA? How much needs to be removed? I would like to ask the experts here, thank you! ! !
The advantage of using ZnO for desulfurization is that it can remove both inorganic and organic sulfur simultaneously. However, the operating temperature of the ZnO desulfurizer has a significant impact on its sulfur capacity, and moreover, ZnO desulfurizers are relatively expensive； If the sulfur content in the feed gas is 3 g/m3, it is advisable to carry out preliminary desulfurization before it enters the PSA unit, in order to reduce the sulfur content in the feed gas to below 300 ppm; of course, the lower the better.
A modified activated carbon desulfurizer developed by the Dalian Institute of Chemical Physics can remove both H2S and COS simultaneously.